- progressive increase in sensory thresholds, an increase in EEG wave amp and decrease in frequency

Stage 1: drowsiness, drifting out of consciousness (only initially)

REM

- rapid eye movement

- oxygen used by the brain is greater than in an awake state

- temporary paralysis keeps us from acting out dreams

- First REM: 5 - 10min

- Final REM: 20 - 50min

- most dreaming occurs here

- motor activity is inhibited

- levels of seratonin and norepinephrine alter during sleep stages

____ responsible for timing of the sleep cycle

Hypothalamus

____ of the hypothalamus regulates _____ during the sleep cycle

- Suprachiasmatic nucleus (biological clock)

- Preoptic nucleus (sleep inducing center)

By inhibiting the brain stem's ___, the ____ puts the cerebral cortex to sleep

- reticular activating system (RAS)

- preoptic nucleus

orexins

- peptides released by hypothalamic neurons to stimulate waking up

slow _1_ and _2_ wars of deep sleep are the result of __3__ firing of thalamic neurons that is normally inhibited during wakefulness by the __4__ of the pons

1. Theta

2. Delta

3. synchronized

4. RAS

Stages of sleep and EEG activity

- Stage 1: decreased beta, less obvious alpha, and emergence of theta

- Stage 2: irregular theta with sudden increase in amp

- Stages 3&4: delta activity predominates, less than 50% in stage 3

REM - similar to stage 1

In NREM, seratonin levels are __1_ where as in REM sleep __2_, ___3__, and in males __4__ is secreted

1. seratonin

2. norepinephrine

3. corticosteroids

4. testosterone

importance of sleep

- slow wave sleep supposed to be restorative

- when deprived of sleep, spend more time than usual in slow wave during next sleep episode

- REM allows brain to analyze day events and work through emotional problems during dream imagery

- Infants: 16 hr

- Adults: 7.5 - 8.5 hr

- REM occupies about 50% total sleeping time

- Stage 4 declines steadily from birth and often disappears totally in those over 40

reverse learning

- hypothesis that in REM sleep accidental, repetitious an meaningless communications must be eliminated form the neural networks by dreaming if the cortex is to remain a well-behaved and efficient thinking system

__1__ and some __2___ suppress REM sleep but not _3___ sleep

1. Alcohol

2. Sleep medications

3. slow-wave

hyperventilation

- since CO2 is lipid soluble and readily crosses the blood-brain barrier and cell membranes, it results in decreased PCO2 (hypocapnia) in brain interstitial fluid and in neurons and glial cells

Hurley and Witkowski showed that _1__ exposure can directly cause an __2__ in __3__ sweat production

- epinephrine

- increase

- eccrine

Cortisol

- drives the resistance reaction to stress during which energy stores are mobilized, gluconeogensis occurs, glucose is conserved along with salts and water (via aldosterone) and the immune system is depressed

- distributes fibers through the rams communicant for sympathetic influence into spinal nerves

sense

- system that consists of a sensory cell type that respond to a specific kind go physical energy, and that correspond to a defined region within the brain where the signals are received and interpreted

adaptation

- process by which a sensory system becomes insensitive to a continuing source of stimulation

vision

- ability to detect electromagnetic energy

cones v. rods

Cones:

- responsible for color differentiation

- fovea: highest visual acuity, pit in macular region of the retina

-4.5 mil

Rods:

- responsible for contrast (light/dark) resolution

- distributed throughout remainder of the retina

- 90 mil

optic disc

- where the nerves and retinal blood vessels enter and exit

- no receptors

- also known as the blind spot

cornea

- light entering comes through here first where it under goes refraction (bending)

- avasuclar transperent epithelial layer

- focusing light on retina (65-75% total focusing power)

- filters UV wavelengths that would damage lens or retina

- "window" over pupil

- light then moves to aqueous humor of anterior chamber

pupil

- light comes from cornea to pupil

- size is controlled by the iris

- brighter the light = smaller the pupil becomes

iris

- muscle fibers that can constrict/dilate the pupil

- back epithelial cells are pigmented with melanin to prevent lightt passing through iris to retina thus it must go through the pupil

lens

- light comes from iris/pupil to here

- avascular

- curvature controlled by ciliary muscles

Accommodation: curvatures adjusts so that the light from objects at different distances can be properly focused on the retina

vitreous humor

- behind lens

- avascular, transparent gel that fills space between lens and retina to provide support

retina

- light sensitive tissue that lines inner surface of the eye

- light passing to rods and cones must first go through ganglion nerve cells and their axons that form innermost surface of the retina

- Muller cells: glial cells that may assist in funneling light to rods and cones

- in relation to two other tunics of the eye - sclera and choroid

cones

- responsible for color differentiation

- fovea: highest visual acuity, pit in macular region of the retina

-4.5 mil

-

rods

- responsible for contrast (light/dark) resolution

- distributed throughout remainder of the retina

- 90 mil

- 100x more sensitive to light that cones and more widely distributed

- responsible for night vision

- many cells converge on single interneuron to enhance light detection and diminish visual acuity and makes peripheral vision sensitive to movement

- sensitve to blue light and insensitive to red light

retinal pigment epithelium

- controls the fluid and nutrient environment of the retina by electively transporting ions and nutrients between blood and retina